I've been trying to solve this problem for a month now.
When I first got the UM2 I was so happy, everything worked fine.
After a couple of prints with different filaments I had major underextrusion, took apart the nozzle, cleaned, 20 times if not more. Support did send a new glass inforced teflon insulator.
That didn't solve it, then I got a complete new hot-end. After this I was able to print but with way higher temperatures and slower speed than before. What used to work fine with 210 degrees, 50/mms, needs to be adjusted now to 220/228 degrees with 80-90% of 50/mms. Also I need to increase the feeder pressure a notch.
The ultimate test came with colorfabb xt, which used to work perfect on 250 degrees and 50/mms but is unable to print nice and shiny threads with 260 degree and 85% of 50mm/s
The question is what is wrong? The temperature is not getting high enough, is this a hardware/software/firmware problem, and how do I fix it?
Thanks in advance, it's opening a whole new area in my brain committed to frustration and despair...
Bas